Diastolic dysfunction (DD) and diastolic heart failure are common disorders associated with significant morbidity and mortality, and the majority of patients with DD have hypertension. Hypertension increases the production of reactive oxygen species (ROS) via endothelial nitric oxide synthase (eNOS) uncoupling, and treatment with tetrahydrobiopterin (BH4) has been shown to prevent eNOS uncoupling. We show that deoxycorticosterone acetate (DOCA)-induced hypertension in a mouse results in DD. The overall goal of this proposal is to determine the mechanisms by which disequilibrium between NO and ROS contributes to DD in this hypertensive mouse model. Aim 1 will examine whether eNOS uncoupling occurs in the hearts of hypertensive mice and if treatment with BH4 preserves diastolic function. Echocardiography and invasive hemodynamic measurements will be used to identify DD and its temporal relation to eNOS uncoupling. Evidence of eNOS uncoupling will be established by measuring BH4 and quantifying eNOS derived NO and ROS. Aim 2 will investigate whether the NADH/NADPH oxidase is responsible for producing the initial ROS to uncouple eNOS and result in DD. We will test whether hypertensive mice lacking p47phox, an essential component for NADH/NADPH oxidase function, will show reduced DD and uncoupled eNOS. Elucidating the mechanisms by which DD develops will be important in developing targeted therapeutic approaches for patients with these disorders. [unreadable] [unreadable] [unreadable]